三相连续环流反应器中氧的液相传质过程

在空气-水-玻璃珠三相连续操作环流反应器中,利用动态溶氧方法研究了表观气速(Ug=0.01~0.13 m/s)、进料浆速(USL=0.001~0.011 m/s)、浆相质量固含率(es=0~30%, w)和固相颗粒大小(dp=59, 200 mm)对环流反应器内氧的液相传质性能的影响. 结果表明,在考察范围内,环流反应器传质系数随表观气速增大而增大,受进料浆速变化的影响较小,随浆相固含率增大呈现先增大后减小的趋势,但在高固含率下(es≥10%, w)的影响不显著;随固相颗粒粒径增大而减小. 同时得到了液相体积传质系数的经验关联式.     

粘度对气液固逆流三相湍动床整体及局部动力学行为的影响

应用开发的微电导探针测试技术,对聚乙烯颗粒(dp=4.01 mm,ps=926 kg.m-3)为固相,水、0.05%(ω)SCMC(羧甲基纤维素钠)及0.2%(ω)SCMC水溶液为液相,空气为气相的逆流三相湍动床(ITPTB)的各相局部含率进行了同时测定,获得了540套局部相含率实验数据.在表观气速ug等于Ug3(颗粒在轴向均匀分布时的表观气速)时,通过对局部固含率(εs)和局部气含率(εg)的径向分布实验研究发现εs呈现床中心处小,床壁处大的分布规律,且在r/R=0.75～0.90范围内有一个极大值峰,极大值峰在径向出现的范围与传统流化床相比增大;εg呈现床中心处最大,床壁处最小的分布规律,与传统流化床相比εg在径向上的非均匀性分布愈加明显.另外,根据εs的轴向分布特性,确定了ITPTB的不同操作流型,得到了相应流型下三个特征表观气速Ug1、Ug2和Ug3,实验考察了液体的粘度(μl)、颗粒静止高度与颗粒和液体总静止高度之比(H0/H0)及液体静止高度(H10)对三个特征表观气速Ug1、Ug2和Ug3的影响规律.     

气液固三相外环流反应器相含率分布与气液流动结构

结合电阻层析成像和差压法,以粒径3 mm的聚氨酯(密度1110 kg/m3)和粒径0.5, 1, 3 mm的玻璃珠(密度2460 kg/m3)为固相、空气为气相、水为液相,在直径0.09 m、高3.1 m的气液固三相气升式外环流反应器中考察了固相颗粒密度、粒径、固相含率对上升管和下降管中气含率的影响. 结果表明,当玻璃珠粒径为0.5和1 mm、表观气速ug>0.10 m/s时环流反应器可达到充分发展段. 以玻璃珠为固相时,气含率随固相含量和粒径增大而增大,从层析图像可见,在r/R=0~0.2处出现非导电相的极大值,且加入大颗粒的下降管中气固含率明显大于加入小颗粒的. 根据电阻层析成像的虚拟像,给出了时间序列的气固混合相的流动特征.     

液体粘度对气液固三相循环流化床颗粒循环速度和流型特征速度的影响

实验的三相循环流化床以玻璃珠 (dp = 0.48 mm, ρs = 2460 kg(m(3) 和苯乙烯颗粒 (dp = 1.45mm, ρs = 1264 kg(m(3)为固相,空气为气相,水、0.05%、0.20% (mass) CMCS (羧甲基纤维素钠)水溶液为液相.实验研究了液体粘度、表观液体速度、表观气体速度、辅助液体速度及颗粒密度对颗粒循环速度的影响.随着液体粘度的增加,颗粒循环速度增加;随着表观液体速度和辅助液体速度增加,颗粒循环速度都增加;随着表观气体速度的增加,颗粒循环速度减小.低密度颗粒系统同高密度颗粒系统相比,低密度颗粒系统能提前从三相传统流型进入三相循环流型.实验还研究了液体粘度对低密度颗粒的起始液体速度和过渡液体速度的影响,为得到三相循环流化床的流型图提供了可靠的依据.     

液固磁稳定床中固含率分布与液相返混特性

固含率分布和液相返混系数是液固磁稳定反应器放大与优化所必需的基础数据。采用床层膨胀高度法、光电法及瞬态点源示踪技术,研究了以SRNA-4催化剂为固相的液固磁稳定床中固含率分布和液相返混特性。试验结果表明,固含率轴向分布基本均匀,径向为“扁-陡曲线”分布。固含率随磁场强度和颗粒尺寸的增大而增大,随液体粘度和空塔液速的增大而减小。轴向液相返混系数随磁场强度和液体粘度的增大而减小,随空塔液速和颗粒尺寸的增大而增大。回归得到了固含率和轴向普朗特准数的关联式,预测值与试验值吻合良好。     

流化床-提升管耦合反应器内固含率的轴向分布及流动发展

在耦合流化床反应器大型冷模实验装置上,考察了不同表观气速下FCC颗粒在耦合流化床内截面平均密度的轴向分布. 结果表明,反应器轴向固含率可分为底部流化床区域和上部提升管区域. 前者的密相区平均固含率随表观气速增大而减小;后者的平均固含率随表观气速Ug增大而增大,Ug<0.58 m/s时固含率分布均匀,Ug=0.70~1.04 m/s时提升管出口出现约束返混区(>8.62 m),Ug>1.16 m/s时提升管底部出现密度重整区(3.82~4.57 m)、加速平稳区(4.57~8.62 m)和出口返混区(>8.62 m). 确定了耦合反应器内提升管区域截面平均固含率的影响参数,并利用实验数据回归了平均固含率的轴向分布经验模型,计算值与实验值吻合较好.     

高长径比气液固三相内环流反应器的流体动力学

在高径比为22的三相内环流反应器中,常温常压下,根据动量平衡原理建立了空气-水-石英砂三相物系的循环液速模型,并建立了上升区气含率、上升区固含率和底部换向区阻力系数模型;考察了在不同颗粒粒径下,表观气速对上升区固含率和液体循环速度的影响。结果表明:当粒径(ds)≤0.3mm时,上升区固含率随表观气速的增加变化呈平缓趋势,当0.3mmds≤1.2mm时,上升区固含率随表观气速的增加而呈先下降后增加的趋势;不同粒径下上升区循环液速均随表观气速的增加而增加;气含率、固含率和循环液速的计算值和实验值吻合较好,其平均相对误差分别为6.32%、4.56%和11.97%。     

高长径比三相内环流反应器中相含率的分布研究

在长径比为22的三相内环流反应器中,常温常压下,以空气-水-石英砂为物系,根据无因次准数建立了气含率、固含率的预测模型,考察了在不同粒径下上升区气含率、下降区气含率和上升区固含率、下降区固含率随表观气速的变化规律和不同固体体积分数下轴向固含率的分布情况。结果表明：不同粒径下上升区和下降区气含率均随表观气速的增大而增大;当粒径（ds）≤0．3mm时,上升区固含率随表观气速的增加呈平缓趋势,下降区固含率随表观气速的增加而增加,当0．3mm〈d。≤1．2mm时,上升区固含率随表观气速的增加而呈先下降后增加的趋势,下降区固含率随表观气速的增加而下降;不同固体体积分数下的固体颗粒的固含率随着轴向高度的增大而变化平缓,能够均匀的分布在反应器中;气含率和固含率的计算值和实验值吻合较好,其平均相对误差分别为6．32％、4．56％。     

液固循环流化床换热器管束的固含率

在二维中试循环流化床中使用组合式固液分布器进行实验,考察下管箱表观液速,主分布器内径、主分布器下插深度,颗粒加入量和粒径对径向管束固含率的影响.结果表明:固含率随主分布器内径、颗粒加入量和下管箱表观液速的增加而增大,随粒径的增大而减小,随主分布器下插深度几乎没有变化;固含率不均匀度随颗粒粒径的增大而增大,随下管箱表观液速、颗粒加入量,主分布器下插深度增加而减小,但达到一定深度后,不均匀度不再随之减小,随主分布器内径几乎没有变化.在综合考虑各影响因素的基础上,提出计算固含率的经验公式,并用实验数据拟合了公式中的参数.     

空气-SRNA-4催化剂磁稳定床的流动特性

床层压降、最小流化速度、固含率及其分布和气相返混系数是气固磁稳定反应器放大与优化所必需的基础数据.采用压降法、光电法及瞬态点源示踪技术试验研究了以SRNA-4催化剂为固相的气固磁稳定床的流动特性.试验结果表明:最小流化速度、最小流化状态下的床层空隙率与磁场强度无关;固含率的径向分布基本均匀;磁场强度的增大抑制了颗粒的运动,使得局部固含率略微增加;空塔气速的增加促进了气固磁稳定床的膨胀,使得固含率减小;粒径较小时,随磁场强度及气速的变化贝克来数(Pe)变化不大;粒径较大情况下,Pe随气速增大而减小,随着磁场强度的增大,先增大后减小.试验获得了最小流化速度、固含率和床层高度的关联式,预测值与试验值吻合良好.     

高长径比环流反应器中气、固含率的轴向分布研究

在高长径比(H/D=22.2)内环流反应器中,常温常压下,以空气-水-石英砂为物系,研究了表观气速和固体装载量对平均气含率、下降区气含率、上升区固含率、下降区固含率的影响,以及上升区气含率、固含率随轴向高度的分布规律.结果表明:平均气含率、下降区气含率随着表观气速的增加而增加,随ω(固体)增大而下降,ω(固体)≤2.6...     

气-液-固三相循环流化床局部相含率分布

应用自行开发的微电导探针测试技术,以玻璃珠(d_p=0.48 mm, ρ_s=2460 kg&#8226;m^-3)和苯乙烯颗粒(d_p=1.45mm,ρ_s=1264 kg&#8226;m^-3)为固相,空气为气相,水及0.05%、0.20% (质量)SCMC(羧甲基纤维素钠)水溶液为液相,对三相循环流化床(TCFB)的各相局部含率进行了同时测定.考察了不同表观液体速度、辅助液体速度、液体黏度及颗粒密度对局部相含率轴径向分布的影响. 在不同操作条件下,获得了1286套局部相含率实验数据. 给出了局部固含率和局部气含率与操作条件、流体物性及床层轴径向位置的关联式,关联式的计算值与实验值吻合较好.     

GAS-PHASE HOLDUP IN A SLURRY-BUBBLE COLUMN

Total and sectional gas-phase holdups are measured in a wide (0.305 m internal diameter) and long (3.7 m) glass bubble column al ambient conditions as a function of superficial gas velocity. Sectional gas holdup values vary along the length of the column and decrease as the height above the gas distributor plate increases in the transitional and turbulent flow regimes. In the discrete bubbling regime, the values are fairly constant in most of the column length except for a small lower portion where the values are significantly smaller than in the rest of the column. This is due to the formation of gas jets at the orifices of the distributor plate. The holdup values are dependent only on the mangitude of gas velocity and do not depend upon how it is approached, i.e., by increasing or decreasing the flow, in the turbulent-flow regime. This is not the case in the discrete and transitional gas-flow regimes. These characteristic variations in gas holdup are explained on the basis of the formation of bubbles in the lower region of the column and their growth by bubble coalescence prior to acquiring a stable bubble size.

Limited experimental data for the three-phase system (air-water-glass beads) indicate that gas holdup decreases as the concentration of glass beads is increased in the mixutre. This is attributed to the increased buoyancy effect in the presence of glass beads which increases the upthrust and hence the bubble velocity which results in the decrease of gas holdup. Total gas holdup data as a function of superficial gas velocity are compared with the predictions of four commonly used correlations and are also analysed in terms of the sectional measured gas-phase holdup data. The inferences that follow are significant.     

MASS TRANSFER AND PHASE HOLDUP CHARACTERISTICS IN THREE-PHASE FLUIDIZED BEDS

The effects of liquid surface tension (42.6 ∼ 72,4 mN/m) and viscosity (1 ∼214mPa • sⁿ), liquid (0.01 ∼0.12m/s) and gas (0.01 ∼0.20m/s) velocities and particle sizes (1 — 8 mm) on phase holdup and mass transfer coefficient ( k_La) have been determined in a 0.142 m-I.D. × 2.0 m-high Plexiglas column. The gas phase holdup increases with liquid velocity, and the rate of increase in gas phase holdup sharply increases with gas velocity in the bed of surfactant solutions. In the beds of 1.0 and 1.7 mm glass beads, the bed contraction occurs whereas in the beds of 2.3 mm glass beads the bed contraction does not occur with an aqueous soltuion of ethanol (σ = 50.4 mN/m). The value of k_La increases with decreasing surface tension (σ ) but it decreases exponentially with increasing liquid viscosity in continuous bubble columns and three-phase fluidized beds. In three-phase fluidized beds with surfactant solutions, k_La increases with gas and liquid velocities and particle size. In three-phase fluidized beds of viscous or surfactant soltuions, k_L,a can be estimated in terms of the energy dissipation rate based on the isotropic turbulence theory and a flow regime map is proposed based on the drift flux theory.     

滴流床反应器内脉冲流下动持液量实验

对气液强相互作用下滴流床反应器内的流体动力学进行了分析讨论 .实验测定了脉冲流流型下的床层平均动持液量 .考察了气液流率、液体黏度、填料材料等因素对动持液量的影响 .根据对滴流床反应器内流体流动机理的分析及实验结果 ,提出了关联脉冲流型式下动持液量的关联式 .该关联式能很好地关联实验数据 ,可用于预测温和型脉冲流下的动持液量     

连续内环流三相反应器局部流动特性

在φ200 mm×2500 mm连续内环流三相反应器内，考察了空气 水 玻璃珠体系反应器内局部流动参数随操作条件的变化规律。结果表明，导流筒内截面平均气含率随表观气速的增大而增大，较之气液两相流，在低固含率时，加入固体对气含率影响不明显，而在较高固含率下，气含率有明显降低，但固体再增加时对气含率变化影响不大。在较低表观气速下，进料浆速对导流筒内气含率轴向分布趋势有一定的影响，但在较高表观气速下影响不大，导流筒内的气含率大于环隙内的气含率且随气速增大差别更加明显，浆相连续有利于气相分散并增大环隙内的气含率。导流筒内循环浆速径向分布呈抛物状，中心高、近壁处低，受进料浆速和入口固含率影响都不大。浆相循环强度最低为20，高可达180。固含率轴、径向分布受表观气速和进料浆速的影响，固含率轴、径向分布基本均匀，随进料浆速增加，反应器内固含率降低。     

Simultaneous effect of particle size and solid concentration on the hydrodynamics of slurry bubble column reactors

The simultaneous effect of particle size and concentration on the total gas holdup of slurry bubble column reactors was investigated in this work. The total gas holdup was measured for air–water–glass beads systems. Three solid concentrations and three particle diameters were used. It was found that increasing particle size at high constant concentration decreases gas holdup. Moreover, increasing solid concentration decreases gas holdup and this decreasing effect is higher for larger particles. Also, solid particles have two effects on hydrodynamics, namely, changing the viscosity and density of the liquid phase as well as hindering the bubbles from rising within the column by the collision phenomenon. Therefore, a novel correcting factor was introduced to correct the gas holdup. The hindering factor considers both the collision efficiency affected by the particle size as well as the solid concentration. A novel correlation was developed to predict the experimental data of the three-phase gas holdup.